As known, rear lights of cars usually consist of rigid rear shell which is substantially tub-shaped, and is structured so to be stably recessed within a dedicated space obtained in the rear part of the vehicle body; of a front lenticular half-shell which is at least partially made of a transparent or semitransparent plastic material, usually colored, and which is arranged to close the mouth of the shell so to emerge from the vehicle body; of a series of cup-shaped bodies having a substantially parabolic profile, which are placed within the rear shell with the concavity facing the front lenticular half-shell, so as to be each aligned with a respective transparent or semitransparent window of the front lenticular half-shell; and of a series of incandescent light bulbs, each of which is placed close to the bottom of a respective cup-shaped body. The inner surface of each cup-shaped body is further mirror-finished so as to reflect/direct the light emitted by the light bulb inside the cup-shaped body towards the corresponding transparent or semitransparent window of the front lenticular half-shell.
In recent years, moreover, the rear lights of cars have increasingly been integrated within the outer profile of the vehicle body, getting to cover the two body edges that connect the rear of the car body to the two side flanks thereof.
Along with the integration of the rear lights within the profile of the vehicle body with the consequent adoption of lenticular half-shells with particularly complex three-dimensional shapes, the major car manufacturers started to require rear lights where the front lenticular half-shell is provided with transparent or semitransparent windows having a narrow elongated shape, which often extend along the whole periphery of the lenticular half-shell.
In order to be able to evenly backlight these band-like transparent or semitransparent windows, the major manufacturers of rear lights for cars decided to replace the traditional incandescent light bulbs with light emitting diode arrays, traditionally referred to as LEDs. LEDs indeed have significantly smaller dimensions than incandescent light bulbs for automotive use, and allow flat light sources to be obtained, which copy the shape of transparent or semitransparent windows to be backlighted, and therefore may be placed right underneath the front lenticular half-shell of the light, thus locally following the profile thereof.
Obviously, using a large amount of light emitting diodes implied a significant increase in the overall costs of manufacturing rear car lights.
In order to at least partially contain this increase in manufacturing costs, some manufacturers decided to backlight the transparent or semitransparent windows of the front lenticular half-shell by means of one or more light-guiding bars or strips made of light-conducting material, with a square section and a nominal thickness of more than 5 millimeters, each of which extends underneath the front lenticular half-shell, at the transparent or semitransparent window to be backlighted, and receives the light from one or more LEDs abutting on one of the two strip ends, usually away from the transparent or semitransparent window to be backlighted.
In other words, the light-guiding bars or strips are recessed within grooves specifically obtained in the rear shell of the light, and are structured so as to channel the light towards the front lenticular half-shell, and then make the light propagating into the strip come out in a controlled and progressive manner close to the half-shell. Thereby, the light-guiding bar or strip is capable of backlighting the transparent or semitransparent window which is right on top.
While the use of light-guiding strips ensures a significant cost saving compared to a massive use of LEDs, it does not allow the front lenticular half-shell, or better the transparent or semitransparent windows of the front lenticular half-shell, to be backlighted with a light having the same intensity as that generated by an array of LEDs, since the light propagating into the body of the light-guiding bar or strip is naturally subjected to scattering and absorption phenomena which quickly reduce the intensity of the light coming out of the strip. These physical phenomena actually prevent the optimal backlighting of transparent or semitransparent windows which are longer than 8-10 centimeters.